How to transform a fixed stroke alternating syringe ventricle into an adjustable elastance ventricle.

Most devices used for bench simulation of the cardiovascular system are based either on a syringe-like alternating pump or an elastic chamber inside a fluid-filled rigid box. In these devices, it is very difficult to control the ventricular elastance and simulate pathologies related to the mechanical mismatch between the ventricle and arterial load (i.e., heart failure). This work presents a possible solution to transforming a syringe-like pump with a fixed ventricle into a ventricle with variable elastance. Our proposal was tested in two steps: (1) fixing the ventricle and the aorta and changing the peripheral resistance (PHR); (2) fixing the aorta and changing the ventricular elastance and the PHR. The signals of interest were acquired to build the ventricular pressure-volume (P-V) loops describing the different physiological conditions, and the end-systolic pressure-volume relationships (ESPVRs) were calculated with linear interpolation. The results obtained show a good physiological behavior of our mock for both steps. (1) Since the ventricle is the same, the systolic pressures increase and the stroke volumes decrease with the PHR: the ESPVR, obtained by interpolating the pressure and volume values at end-systolic phases, is linear. (2) Each ventricle presents ESPVR with different slopes depending on the ventricle elastance with a very good linear behavior. In conclusion, this paper demonstrates that a fixed stroke alternating syringe ventricle can be transformed into an adjustable elastance ventricle.